1. Field of the Invention
The present invention relates to a portable radio communication device, and more particularly to a portable radio communication device with an antenna that is extendable for use and retractable for storage, and a loaded antenna for use on a portable radio communication device.
2. Description of the Related Art
Recent years have seen widespread use of portable radio communication devices such as portable telephone sets. Such portable radio communication devices are required to be small in size and light in weight, and have antennas that are extended when in use and stored when not in use.
On small-size portable radio communication devices, the antenna is positioned closely to those components, including the housing of the device and the printed-circuit board in the housing, which affect the characteristics of the antenna. When the antenna is stored, it is positioned in the housing close to the printed-circuit board, resulting in a reduced antenna gain. During storage of the antenna, the gain of the antenna is also lowered because the effective length of the antenna is smaller.
To meet the requirements for small sizes and low weights, there have been demands for portable telephone sets, cordless telephone sets, and low-power radio communication devices which have smaller and lighter circuit components and batteries, and smaller and higher-performance antennas.
Generally, portable radio communication devices are designed to radiate a predetermined amount of electrical energy while the antenna is being extended.
The user of a portable telephone set extends its antenna before making an outgoing call through the portable telephone set. However, when an incoming call from another party arrives, the antenna has usually been stored in the housing of the portable telephone set. Upon arrival of the call, the user extends the antenna for use.
More specifically, when a portable telephone set receives an incoming call from a central office, it is necessary for the portable telephone set to transmit a response signal to the central office in response to the incoming call for the purpose of confirming a telephone connection that has been established between the central office and the portable telephone set, so that a ringing tone can be generated indicating the incoming call to the user.
When the antenna of the portable telephone set is stored at the time the incoming call arrives, however, since the gain of the antenna is lowered, the electric energy radiated from the antenna is at a low level. If the portable telephone set is distant from the central office, then the response signal which is transmitted from the portable telephone set in response to the incoming call may not reach the central office, and the portable telephone set may not generate a ringing tone. Therefore, since the characteristics of the storable antennas are degraded when the antennas are in storage, it has been desired to mechanically improve the characteristics of the storable antennas.
Heretofore, most portable telephone sets employ whip antennas. Attempts to make portable telephone sets smaller in size have also resulted in the use of planar antennas, top-loaded antennas, small-sized whip antennas, and bottom-loaded antennas.
The bottom-loaded antennas have find use as fixed antennas, but have not been used as antennas that can be retracted or contracted for storage.